Add TUI kanban board, review workflow, and new task statuses

Replace task statuses (pending/running/succeeded/failed/cancelled) with
a kanban workflow: todo → in_progress → in_review → done/wontdo.

When a non-review agent task completes, the API auto-creates a child
review task and moves the parent to in_review. Only humans can move
tasks from in_review to done/wontdo via the TUI.

New components:
- cmd/tui: bubbletea kanban board with $EDITOR integration
- POST /api/v1/tasks/{id}/complete: agent completion callback
- Operator --api-url flag for completion callbacks
- ProviderQueue sets tasks to in_progress on pickup
- AgentTask reconciler calls /complete on job finish

cmd/tui/main.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"git.unkin.net/unkin/forgebot/internal/tui"
+)
+
+func main() {
+	apiURL := flag.String("api", "http://localhost:8000", "forgebot API base URL")
+	flag.Parse()
+
+	if v := os.Getenv("FORGEBOT_API_URL"); v != "" {
+		*apiURL = v
+	}
+
+	m := tui.NewApp(*apiURL)
+	p := tea.NewProgram(m, tea.WithAltScreen())
+	if _, err := p.Run(); err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
+}